I often neglect to bear bag also, even in areas with black bear sightings on the regular down here in WNC.
Honestly, I'm curious if it has more to do with my diet (vegetarian), and food choices on the trail, but I rarely even have rodents bother my food when in the occasional AT shelter. I've never had a bear go after my food. Maybe it's because I like all my stuff at about a 8 or 9 on the spiciness scale, or maybe they just hate the smell of curry cashews. ;)
I have recently started taking a small or medium OPSack though, just for good measure. I wish they had an interim size though, or a pleated bottom. The medium at 12x20 is too big and weighs like 40something grams, and the small is too small often.
Still, weight really has nothing to do with why I often don't hang my food. It's almost entirely due to the hour long process of finding an appropriate tree in my area, getting a line up to the only useful branch in a mile radius, after multiple hang-ups, finally getting a decent hang, usually, in the dark, as Ike mentions.